Sizu Riatto
Flush Hour · Chapter 5

Hot Water

Know how long the pot takes and what the heat costs before you light the hob. Q = m × c × ΔT turns liters and degrees into kWh, minutes and money.

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Opens on the book's tub. Change any number to your own and press Calculate.

The water

The temperatures

The power and the meter

Enter the straw, the water and the temperatures, then press Calculate.

The formula

  • Water = dry straw × the water ratio (the book: 18 L a kg); a batch = water ÷ batches. 1 L of water weighs 1 kg
  • Heat Q = m × c × ΔT: kg of water × 4.186 kJ a kg a °C × the rise in °C; kWh = kJ ÷ 3,600
  • Minutes with no losses = kJ × 1,000 ÷ watts ÷ 60. Real pots lose heat: efficiency = the heat ÷ the meter's kWh
  • °F = °C × 9 ÷ 5 + 32; a temperature difference in °F = the difference in °C × 1.8
  • Pasteurize (60 to 80 °C) is not sterilize (121 °C under pressure): it thins out competitors, it does not kill everything
The book's worked example, Chapter 5. 1.80 kg of dry straw × 18 L = 32.4 L, three batches of 10.8 L (2.85 gal) in a 16 qt (15 L) stockpot. Heating 15 → 75 °C (167 °F) takes 10.8 × 4.186 × 60 = 2,712.53 kJ = 0.7535 kWh a batch, 2.26 kWh for all three; at 2 kW with no losses, 22.60 minutes a batch. The meter says 3 kWh, so 75.35% reached the water. Then hold 70 °C (158 °F) for 90 minutes.
Check it. Time your own pot from tap to 75 °C with a probe thermometer: within 10% of your call scores 2 points.

Honest limits. The book's hold, 70 °C for 90 minutes inside a published range of 65 to 75 °C for 1½ to 2 hours, is one method among several; follow your spawn supplier's instructions too. A pressure canner is used only by its maker's instructions. Lime soaking is caustic: gloves and goggles. The book's tub, its straw and its harvests were worked out on paper from published figures, not grown by us: weigh your own. Prices are illustrative, as seen in November 2026 (US mid prices, with UK beside where they differ), shown without a currency sign; put in your own. No yield or profit is promised. Everything stays in your browser: no sign-up, nothing stored.